Telephone-exchange system



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TELEPHONE- EXCHANGE SYSTEM Aug. 7, w23.

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TELEPHONE EXCHANGE SYSTEM Filed June 9 1920 A. E. LUNDELL ET ALTELEPHONE EXCHANGE SYSTEM'v l Filed June 9. 1920 10 Sheets-Sheet 10/hx/em fors /ben E Lande/L Edgar H. C/m/K Patented 7, H9323,

muren stares tentent cornice ALBEN E. LUNDEL'L, OF CHlICAG-O, JULLINJIS,AND EDGAR EL CLARK, 0F BJICHMND mild), NEW YRK, .LSSEGNORS TO WIESTERN'ELECTRC COMPANY, IENCORPORTED, 0F NEW YORK, 'El'. Y., .d COBJPRATIEONUJF NEW YUEK.

TELElPlBmNlE-EXCEMGE SYSTEEM'.

Application tiled June 9,

T o all fwhom 'it may concern:

Be it lmown that we, Armin lE. llannnnnr. and Encan lill. (linnn,citizens of the United States, residing at Chicago, in the county ofCoolr` and State of llllinois, and at Richmond Hill, in the county oiQueens and State of New York, respectively, have invented certain newand useful improvements in 'llelephone-Exchange Systems, of which thetolio lowing is a lull, clear, concise and exact descrlption.,

rlFhis invention relates to telephone exchange systems in whichconnecting oper ators are employed for extending connections, withindicating mechanisms at such operators positions to identity thedesignatlons or' desired lines.

lin systems where certain oces are equipped with mechanical switchingapparatns, whereas other oces employ manual operators tor establishingcoections, it is ,-ounddesirable that the manualoperators loe given theinformation required for them to extend or complete coections incomingfrom the mechanical oiltce without the necessity of communicating orallywith the calling subscriber or with other operators. 'llo this end,each. operators position, in the manual oce, is provided with callindicator mechanism, including a set of numberindicating devices, whichis operated automatically under the control ot registering mechanism inthe' mechanical oce to inform the manual connecting operator oit thenumber and character of the required connection. llt is customary, inarrangements of this character, to provide each trunlr circuit incomingto an operators position from the distant mechanical omce with a signal4o lamp, the illumination of which advises the operator that a call isawaiting her attention on the corresponding trunlr. At her convenienceshe associatesr the calling trunk with the common indicating mechanismat her position, and thereupon the wanted designation is set up anddisplayed betere the operator, who proceeds to complete the connection.

Where no attempt is made to secure a uniiaao. serial no. aantal.

formity in the distribution of calls to the several operators in an oceof this character, it may frequently occur during busy hours of the'day,that an excessive number of calls simultaneously appear on the trunks atany given operators position, while at the two positions adjacentthereto only a comparatively few calls are awaiting attention. in orderthat the completion of calls shall not be unduly delayed on thisaccount, provision is made whereby the adjacent operator on either sideof a home operators position may assist the home operator by attendingto some of the calls at her position.

Accordingly, it is the object of this invention to provide, in a systemof the foregoing character where operators positions are each equippedwith a group of trunks and an indicating mechanism, means whereby oneoperator may cause to be set up, on the indicating mechanism at herposition, the designation of calls appearing on trunks at otherOperatoris positions.

A feature of the invention/relates to an arrangement whereby thecurrentimpulses incoming over the trunk circuit at a home operatorsposition, which normally serve to record the desired designation on theindicating mechanism at such position, may be directed to an adjacentposition for the purpose of recording the designation on the indicatingmechanism at said adjacent position.

Another feature relates to the provision of two assignment keys for eachtrunk circuit at an Operators position; one of which, when operated,associates the corresponding trunlr` with the indicating mechanism atsaid position and causes the incoming impulses to set such mechanism inaccordance with the designation concerned; the other of which keys, whenoperated associates said trunk with the indicating mechanism at adiderent operators position and causes the incoming impulses to recordthe designation on the mechanism at said latter position.

Still another feature relates to the provision of a signal individual toan incoming trunlr which operates in one distinctive trated in Fig. 11,disclose so much of a tele` phone system which embodies the invention,as is necessary to an understanding thereof.

Fig. 1 shows the incoming end of an interoiiice trunk circuit at amechanical oiiice and the details of a district selector switch in whichsaid trunk line terminates. Fig. 2 shows in detail the circuits of anolice selector switch in the mechanical oilice.

Fig. 3 shows a trunk finder switch, com- `mon to a plurality of incomingtrunk circuits, for associating an idle register sender with a desiredtrunk.

Fig. 4 shows a sender for controlling the operation of the selectiveswitches, comprising a circuit changing sequence switch and a oup ofcounting relays.

ig. 5 illustrates a plurality o sets oi keys at an operators position,and a series of corresponding registers arranged to be positioned underthe control of said keys for determining the selective operationsinvolved in the extension of a connection.

Fig. 6 shows a switch and associated circuits for transmitting series ofcode impulses, according to the variable settings of the registers, tooperate a call-indicator mechanism at a distant olice.

Fig. 7 shows in detail a trunk circuit incoming from the mechanicaloiice to a manyual operators position in a distant oilice.

Fig. 8 shows a call-indicating mechanism at the manual operatorsposition arranged to be associated with any of the trunk circuits atsuch position and operated in response to the code impulses sent over acalling trunk lfrom the mechanical oiflce.

Fig. 9 shows the .selecting relays and numerical lamps of thecall-indicator for visually informing the manual operator of thedesignation of a called line.

Fig. 10 illustrates diagrammatically a trunk circuit similar to thatshown in F ig.

' 7, incoming from the mechanical office to an operators positionadjacent to the position at which the first mentioned "trunk ap ears.Below the horizontal broken line in th1s figure there is illustrated thecall-indicator mechanism at` the adjacent operators position which issimilar in all respects to the one shownin detail in Figs. 8 and 9.

Fig. 11 shows how the iguresof the drawing are to be arranged to connectthe circuits of the several figures.4

. General description of system and apparatus.

In the establishment of a connection in the system, disclosed, threedifferent oilices are to be considered; a calling manual oflice,

-where the call first originates; the tandem mechanical oiiice, throughwhich the connection is extended by means of automatic the operatortherein communicates with the* operator in the mechanical oiiice bymeans of an order wire and requests the assignment of an idle trunk. Theoperator at the mechanical office assigns an idle trunk, such as trunk100, 101, and depresses the individual assignment key 108. Thedepression of key 108 initiates the operation of the trunk finder shownin Fig. 3, which associates the7 register 4sender shown in F igs. 4, 5and 6, with the assigned trunk. The operator in the mechanical oiiicehaving` been verbally informed of the name of the desired oiiice and thenumber of the called line insuch oiiice, proceeds to set up thedesignation on the keys at her position. The selective operations of thedistrict and oiiice switches, which jointly serve to select an outgoingtrunk to `any one of. a plurality of distant oiices, are controlled bythe settings of the four registers 500, 510, 520 and 530. Each of thevarious combinations of settings that these registers may take,determines the selection o a group of trunks leading to a y particulardistant oiiice. .For convenience,

therefore, a single oilice key is provided to ll0l required number ofofice selections. In ad- Y dition to the oliice4 keys, the operatorsposition is equipped with four sets of numerical keys, ten keys in eachset, for. setting the .numerical registers 540, 550, 560 and 570.

After the operator has depressed the proper combination of oice andnumerical keys the district and oiiice selectors are operated and theconnection extended over a trunk, suchy as 700, 701, to an operatorsposition in the desired manual iiiee. The

loperator in the.terminating oice is informed that a call is awaitingher attention, by the illumination of a lamp individual to the incensetrunk circuit. As soon as the operator has completed the extension ofsuch calls as may have previously been directed to her position, sheattends to the call appearing o n the trunk 700, 701, by depressing theind1- vidual assignment key. The depression of this key operates toassociate the call-indicator mechanism at her position with the callingtrunk circuit. Code impulses are then sent over the trunk in accordancewith the settings of the numerical registers oi' the mechanical otliceto select the pro er combination of numerical lamps. rllhe i uminationof the indicator lamps at the operators position informs her of thenumber of the called line and the connection is completed by insertingthe terminating plug of the trunk circuit in the proper jack.

lt may happen that due to the simultaneous appearance of a large numberof calls at a given position, the operator is unable to attend to allthe calls with the necessary dispatch. According to the principles oitthis invention, the adjacent operator on either side is able to assistthe home operator whenever she becomes overtaxed in her duties, byattending to some of the calls at the home position. For this purpose,each of the trunks at a position is provided with a team assignment key.'llhe adjacent operator, observing the presence of a larger number oitcalls at the home position than the home operator can convenientlyhandle, reaches across and depresses the team assignment key ot acallingtrunk. 'llhe depression ot 'the team key `,serves to associatethe Calling trunk at the home position with the callindicator mechanismat the adjacent operators position. The incoming code impulses are,therefore, directed to the indicator mechanism at the adjacent orhelping-out operators positionand the designation of the desired linedisplayed on the numerical lamps at such adjacent position. yll`headjacent operator then seizes the plug ot the calling trunk circuit atthe home operators position and inserts it in the jack of the calledline. As will be more fully explained hereinafter, supervision of a callthus completed by an adjacent operator, remains under the care of thehome operator in the same manner as calls normally attended to by thehome operator.

contacts .contained in each of such figures. ln Figz, the contactscontained within the spaces set 0E by the vertical broken lines, arecontrolled respectively by the correspondingly located sequenceswitches.

Detailed desme'ptonf-dz'sposz'ton of @all by the home operator.

the connection is extended, is comparatively unoccupied and abletoattend to the call without the vassistance of the adjacent operator.rJlhe call having been originated in a distant manual oHice and thetrunk 100, 101 having been assigned for use, the operator in themechanical office depresses the assignment key 108.- A circuit is thencompleted from ground through the contacts of key 108, right-handcontact 109 (1),. winding of sequence switch magnet 110, to battery andground. Sequence switch 110 moves out of its normal position 1 intoposition 3. ln position 3 of sequence switch 110 a' circuit isestablished from battery, through the winding of the trunk tindersequence switch 310, right-hand contact 317 (1) conductor 329, lower`right-hand contact 113 V(3), upper right-hand contact 113 (3), backcontact and letthand armature of rela 111, upper left-hand contact 121(2 to 1 lower right-hand Contact 121 (1 to 12), to ground.F 'lhe trunkfinder sequence switch 310 leaves its normal position and advances intoposition 2. iin position 2 of sequence switch 310, a circuit iscompleted trom battery, through the winding of the up-drive power magnet320, contact 31d (2), back contact and left-hand armature of relay 311,to ground. Magnet 320 energizes and the brush shaft 312 of the trunkfinder is moved upward to selectL the set of terminals individual to thetrunk 100, 101. When the test/brush 307 of the trunk finder reaches theterminal 302, a circuit is closed from battery, through the winding ofrelay 311, left-hand contact 328 (2), brush 307. terminal 302, conductor139, lower contact 122 (3), upper contact 122 (2 to 3),back contact andouter right-hand armature of relay 111, upper lefohand contact 119 (2 to11), lower left-hand contact 119 (2 to t), to ground. Relay 311 attractsits armatures and opens the circuit of the 11p-drive power magnet 320,causing the brushes of the trunk finder to stop in engagement with thedesired set of terminals. Relay 311 locks up in a circuit n from batterythrough the winding of said relay, right-hand contact 328 (2 to 17),right-hand armature and contact of relay Cdl L depresses No. 4- key 311,brush 309, terminal 304, conductor 141, lower left-hand contact 114 (2%to 16), upper right-hand contact 114 (2 to 129;) to ground. Relay 311also completes a circuit from ground through its left-hand armature andfront contact, right-hand contact 315 (2), winding of sequence switch310, to battery and ground. Sequence switch 310 moves out of position 2and into position 6. In position 6 of sequence switch 310, a circuit isclosed from ground, through contacts 313 (6), brush 308, terminal 303,conductor \145, left-hand contact 115 (3), right-hand winding of relay111, to battery and ground. Relay 111 energizes and completes a circuitfrom battery, through 'the winding of sequence switch 110, lowerletthand contact 112 (3), upper {right-hand contact 112 (2 to 12), frontcontact and left-,hand armature of relay 111, upper lefthand contact 121(2 to 17), lower righthand contact 121 (1 to 12) to ground. Sequenceswitch 110 advances from position 3 into position 5, opening the circuitof relay 111, which thereby deenergizes.

An idle register senderl is now associated with the calling trunkcircuit 100, 101.

The operator, having been informed over the order wire of the wanteddesignation, depresses the key 580, which determines the selection ofthe desired oiiice. Furthermore, she sets up on her keyboard thenumerical designation of the-called line in that oice. 'Ifheseveraloiiice and numerical keys at the operators position are arranged to beretained in their actuated position by means of locking magnets `503,513, 523, 533, 544, 554, 564 and 574i Assuming that the number of thewanted line is 4432, the operator 543 in the thousands row, No. 4 key553 in the hundreds row,

.No.3 key 563 in the tens row and No. 2

keyL` 573 in the units row. Assuming the code pertaining to olice key580 to be 1223, the contacts 'of this key are wired to contactsi of thefour oilice registers 500, 510, 520 and 530, closed respectively inpositions 1, 2, 2 and "3.

As soon as the trunk finder sequence switch 310 reaches \position 5,parallel circuits are completed thrugh'the windings of the registers500, 510,` 520, 530, 540, 550,

560 and 570, back contacts and right-hand armatures of the` respectivestop relays 501, 511, 521, 531, 541, 551, 561, and 571, to the commonconductor 582, contact 326 (5 to-6),

to ground. These registers are all ener-l gized in the circuits tracedand commence to rotate. When register 500 reaches position 1, a circuitis closed from battery through the winding of relay 501, contact 502(1), left-hand contacts of key 580, to ground. When register- 510reaches position 2, a circuit is closed from battery through thewindingof relay 511, contact 51.2, (2), left-hand contacts of key 580,to

ground. In position 2 of register 5,20, a circuit is closed frombatltery through the winding of relay 521, contact 522 (2), righthandcontacts of key 580, to ground. In position 3 of register 530, a circuitis completed from battery, through the winding of relay 531, contact 532(3), right-hand con` tacts of key, 580, to ground. Relays 501, 511,521,' and 531 energize in the circuits traced and open the operatingcircuits of the four oliice registers, causing them to stop in theirrespective positions. When the numerical registers 540, 550, 560 and 570reach positions 4, 4, 3, and 2 respectively, similar circuits are closedthrough contacts 542, 552, 562 and 572, for the stop relays 541, 551,561 and 571, and in a similar manner, the operation of these relaysopens the circuits of the numerical registers, causing them to cease torotate. With all the stop relays' energized a series circuit is closedfrom ground, through the front contacts and left-hand armatures of saidrelays, conductor 583, lower right-hand contact 316 (6), winding ofsequence switch 310, to battery and ground. Sequence switch 310 advancesfrom position 6 into position 10. As sequence switch 310 passes throughpositions 7 and 8 a circuit is closed from ground contact 330, (7 to 8),conductor 584,- through the windings of the holding magnets 503, 513,523, etc. in parallel, to battery and ground. These magnets energize andrelease the depressed keys of the operators keyboard. The registers donot restore, but remain in the position last used. In position 10 ofsequence switch 310, a circuit is closed from Ibattery, through thewinding of the sender sequence swltch 410,"r lower right-hand contact407 (1), contact 331 (10), to ground. The sender sequence switch movesfrom its normal position into position 4.

The office and numerical designations are now recorded on the registersof the sender and the selective operation of the district and oiiiceswitches may be proceeded with. Accordingly, the fundamental circuit forcontrolling the brush selection of .fthe district switch is establishedas follows: battery, through the right-,hand winding of relay 111, lowerleft-hand contact 118 (5),

-lower right-hand Vcontact 118 (5 to 8), conllF nuancer,

left-hand armature of relay 111, upper lefthand contact 121 (2 to 17),lower ri ht-hand contact 121 (1 to 12), to ground. equence switch 110advances into position 6. Relay 111 remains energized in position 6 otsequence switch 110 by means of a circuit from battery, through theright-hand winding, contact and inner right-hand armature of said relay,upmr lett-hand Contact 118 (3 to 10), lower right-hand contact 118 (5 to8), and thence to ground over the fundamental circuit as described. 1nposition 6 of sequence switch 110 a circuit is closed from batterythrough the winding of the updrive magnet 127, lower right-hand contact112 (6), upper right-hand contact 112 (2 to 12), front contact andleft-hand armatureot rela 111, upper lett-hand contact 121 (2 to 17lower right-hand contact 121 (1 to,.12), to ground. The power magnet 127energizes and causes the upward movement et the brush shaft 129. Foreach brush tripping position passed over by the brush shaft 129, theauxiliary brush 130 makes engagement with a metallic segment of the,

brush selecting commutator 132 and completes a circuit rom battery,through the right-hand winding, contact and inner right-hand armature ofrelay 111, upper lett-hand contact 118 (3 tol 10), lower righthandcontact 123 (5% to 6), commutator 132, brush 130 to ground. The closureot this circuit maintains the energization of relay 111 and at the sametime shunts out the stepping relay 400 in the fundamental circuit.

17V hen stepping relay 400 first energizes in series with relay 111 itcompletes a circuit from ground through its contant and armature, lowercontact 402 (4), conductor 585, Contact 504 of register 500 closed inposition 1, conductor 505, and thence to conductor 426 (Fig. 4) armatureand back oontact of the No.' 1 counting relay 422, winding ot No. 1counting relay 423, to battery and ground. Relay 423 energizes andcloses a circuit -from battery through the windings of relay 423 and422, contact and armature of relay 423, contact 404 (4) to ground. Relay422, however, dcesgnotl energize at this time since it is shunted out bythe direct circuit to ground closed at the armature and contact of thestepping relay 400. .As soon as the brush 130 encounters the lirstmetallic segment of the brush-selecting commutator, theA stepping relay400 deenergizes, and removing the shunt around relay 422, permits this,relay to energize in series with relay 423. @n the next energization ofthe-stepping relay 400, as brush 130 reaches an insulated segment, thestepping circuit, closed at the armature and contact of relay 400, is

extended by way of conductors 505 and 426,

" armature and front contact of relay 422,

right-hand armatureA and contact of relay 420, ding of relay 421, tobattery and und. Relay 421 energizes and completes a circuit trombattery through the windings of relays 421 and 420 in series, contactand armature ot relay 421, contact 404 (4), to ground. As soon asstepping relay 400 is again shortcircuited the shunt is removed `fromaround the winding of relay 420 and this relay energizes in series withrelay 421. The operation ot the 0' counting relay 420 opens thefundamental circuit at its outer left-hand armature and closes at itsinner lett-hand armature a circuit including upper right-hand contact407 (4), for driving the sender sequence switch 410 out of position 4and into position 6. Sequence switch 410, passing from position 4toposition 6, opens at its contact 404, the locking circuit of thecounting relays, permitting them to release. As soon following theenergization ot' the 0 counting relay 420, as the brush 130 reaches thenet insulating segment, relay 111 is deenergized and opens the circuitof the 11p-drive power magnet 127, terminating the movement ot the brushshaft. Relay 111 also completes a circuit from battery through thewinding of sequence switch magnet 110, upper left-hand contact 113 (6),upper righthand contact 113 6), back contact and lett-hand armature orrelay 111, upper left-hand contact 121 (2te 17), lower righthand contact121 (1 to 12), to ground. Se-

uence switch 110 advances into position 7. circuit is now closed frombattery, through the winding of vthe brush-tripping magnet 128, upperand lower right-hand contacts 121, to nd. rllhe magnet 128 energizes andprepares tor the tripping of the selected set of brushes on the nextupward movement of the brush shaft.

The fundamental circuit is again established from battery through theright-hand winding of relay 111, lower left-hand contact 118 (7), lowerright-hand contact 118 (5 to 8) and thence as above traced, through thewinding of the stepping relay 400, to fr und at contact 403 closed inposition 6. elay 111 becomes energized and completes a circuit frombattery, through the winding of sequence switch ma et 110, lowerletthand contact 112 (7), upper right-hand contact 112 (2 to 12), tirentcontact and letthand armature ot relay 111, to ground at contact 121.Sequence switch 110 advances into position 8 while relay 111 remainslocked up over its right-hand winding in the manner explained. Relay 111a circuit trom battery,- through the vending of the up-drive powermagnet 127, lower right-hand Contact 112 hand contact 112 (2 to 12),front contact and left-hand armature of relay 111 to ground at contact121. Magnet 127 energizes and causes the brushIl shaft 129 to more,upward in the group selecting move- (8), upper rightl ment. Eacli timethe brush 130 engages a metallic segment of the group-selectingcommutator 133, a circuit is closed from battery through the right-handwinding, con- 'tact and inner right-hand armature of relay When relay400 energizes in Series w1th` relay 111 a circuit is closed from ou'ndthrough the contact and armature o' relay 400, upper con-tact 402, (6),conductor 586 contact 514 of register 510 closed in position 2,conductor 515, and thence to conductor 427 (Fig. 4), armature and backcontact of relay 424, winding of relay 425, to bat tery and ground.Relay 425 energizes and prepares a circuit for relay 424, which latterrelay becomes energized as soon as the stepping relay 400 is shunted outby the groupselecting commutator of the switch. For each group ofterminals passed over by the brushes 142, 143 and 144, the step; pingrelay 400 is operated and a pair of counting relays energize and lockup. When the 0 counting relay 420 is finally energized, the fundamentalcircuit is opened and a circuit closed including the upper righthandcontact 407 (6) for driving the sender sequence swi-tch into position10. In passing from position 6 to position 10, contact 404 of sequenceswitch 410 is opened to permit the releaseof the energized countingrelays.

As'soon after-'the opening of the fundamental circuit Aby the 0countingrelay 420, asthe brush 130 engages an insulating segment of thecommutator 133, relay 111 is deenergized.- 'Relay 111 opens the circuitof power magnet 127, causing the switch to come to rest in operativerelation to the desired group of terminals. Relay 111 also closesacircuit from battery through the winding of sequence switch ma et 110,upper left-hand contact 113 (8), upper righthand contact 113 (8), backcontact and lefthand armature of relay 111, to ground at contact 121.Sequence switch 110 moves out of position 8 and into position 9.

In position 9 of sequence switch 110, re-

lay 111 is immediately energized by means of a circuit from battery,through the righthand windinoF of said relay, lower left-hand contact118 9 to 9%) upper left-hand `contact 123 (9 to 9%), to ground.V Relay111 completes a circuit from battery through the winding of sequenceswitch 110, lower lefthand contact 112 (9), upper right-hand contact 112(2 to 12), front contact and lefthand armature of relay 111, to groundat contact 121, driving sequence switch 110 into posltion 10. Providedthe first trunk in" the selected group, on the terminals of which the'10 and into position 11.

brushes 142, 143 and 144 are now standing, is busy, relay 111 remainsenergized in the following circuit: battery, through the lefthandwinding of said relay, contact 120 (9 to 10, front contact and outerright-hand 12), front contact and left-hand armature ofrelay 111, toground at contact 121. Magnet 127 is energized and brush shaft 129 movesupward in .the trunk-hunting operation. When the test brush 144encounters an idle test terminal, the holding circuit of relay 111 isopened and this relay releases itsl armatures tovopen the circuit of thepower magnet 127. Relay 111 also closes a circuit from battery, throughthe winding of sequence' switch magnet 110, upper left-hand contact 113(10), upperrlght-hand vcontact 113 (10), back contact and left-handarmature of relay 111, to ground at contact 121. Sequence switch 110moves out of position 110, on reaching position 10%, c oses its lowerleft-hand contact 119 to sup ly a busy ground potential 'over testbrusii 144 to the test terminal 136 of the selected trunk.

In position 11 of sequence switch 110 the fundamental circ-uit isextended through to the office selector shown in Fig. 2 for controllingbrush-selection at this switch. The fundamental circuit may be tracedfrom battery through the right-hand winding of relay 211, lowerleft-hand contact 203 (l), left-hand contact 208 (1 to 4), conductor200, terminal 134, brush 142, lower left-hand Se uence switch` contact123 (11), lower right-hand contact 118, (11), conductor 137, terminal300, brush 305, upper contact 324 (10), winding of stepping relay 400,contact and outer lethand armature of relay 420, upper righthand Contact403 (10) lower right-hand contact 403 (10), upper contact 323 (10),brush 306, terminal 301, conductor 138, lower contact 125 (11), brush143, terminal 135, conductor 201, contact 230 (1 to 4), to ound. Relays211 and 400 become energize in this circuit. Relay 211 closes a circuitfrom battery, through the winding of sequence switch magnet 210, lowerleft-handcontact 204 (1) .front contact and left-hand armature of r^elay 211, to ground. Sequence Switch 210 moves from position 1 intoposition 2. Rea

aaeaoea from battery, through the right-hand winding, front contact andinner right-hand armature, outer right-hand armature and contact of saidrelay, lower right-hand contact 203'(1 to 4), and thence to ground asdescribed. Relay 211 closes a circuit from battery through the Windingof the up-drive power magnet 213, right-hand contacts 205 (2), frontcontact and left-hand armature of relay 211, to ground. Magnet 213energizes and causes the upward movement of the brush shaft 215 in thebrush-selecting operation.y F or each brush-tripping position of theshaft 215, brush 218' engages a metallic segment of the brush-selectingcommutator 219. A circuit is thereby closed from battery, through theright-hand winding, front contact and inner right-hand armature of relay211, outer right-hand armature and front contact of said relay, lowerright-hand contact 203 (1 to 4), upper righthand contact 203 (1% to 2),commutator 219, brush 218, to ground. This circuit maintains theenergization of relay 211 and causes the stepping relay 400 in thefundamental circuit to be shunted.

`When relay 400 first energizes in series with relay 211 a circuit isclosed from ground, throu h the contact and armature of relay 400, owercontact 401 (10), conductor 587, Contact 524 of register 520 closedl inposition 2, conductor 525, and thence to conductor 427 (Fig. 4),armature and back contact of the No. 2 counting relay 424, winding ofrelay 425, to battery and ground. Relay 425` becomes energized andprepares a locking circuit for itself in series with relay 424. )Whenbrush 218 encounters theA first metallic segment of commutator 219, thestepping relay 400 is shunted and relay 424 becomes energized. Thestepping circuit closed at the armature and contact of relay 400 is nowextended over the armature and front Contact of relay 424 to the nextcounting relay '423. When the proper number of brush-tripping positionshave been passed over by the brush 218, the 0' counting relay 420 isenergized to open the fundamental circuit.A Relay 420 also closes acircuit including its inner left-hand armature and contact and upperright-hand contact 407 (10) to drive sequence switch 410 into positionV12. As soon after the fundamental circuit is opened by the 0 countingrelay, as brush 218 moves on to an insulating segment of contator 21,9,relay 211- becomes deenergized. This closes a circuit from battery,through the winding of sequence switch magnet 210, lower right-handcontact 204 (2), back contact and left-hand armature of relay 211 toground. Sequence switch 210 e advances from position 2 into position 3.Tn position 3 of sequence switch 210, a circuit is closed from batterythrough the winding of the brush-tripping magnet 214, lower left-handcontact 200 (3 to 7), to ground. Magnet 214 energizes preparatory totripping the selected set of brushes on the next upward movement of theshaft 215.

With sequence switch 210 in position 3 and sequence switch 410 inpositionV 12 the fundamental circuit is again closed in the mannerdescribed for controlling the groupselecting operation of the ofoeswitch. Bes lay 211, upon energizing, closes a circuit from battery,through the winding of sequence switch ma et 210, lower left-handcontact 204 (3), front contact and left-hand armature of relay 211, toground. Sequence switch 210 advances into position 4, and relay 211remains energized in the circuit leading through its right-handarmatures and the lower right-hand contact 203. Relay 211 completes acircuit from battery through the winding of the 11p-drive magnet 213,right-hand contacts 205 (4), to ground at the front contact andleft-hand armature of relay 211. The brush shaft 215 is moved upward andfor each group of trunlr terminals traversed the brush 218 engages ametallic segment of the group-selecting coinmutator 220. A. circuit isthereby closed from battery, through the right-hand winding, frontcontact and inner right-hand armature of relay 211, outer right-handarmature and contact of relay 211, lower righthand contact 203 (1 to 4),upper left-hand contact 203 (3;3; to 4), commutator 220, brush 218, toground. This circuit holds the relay 211 energized and causes theshunting of the stepping relay 400 in the fundamental circuit.

When relay 400 cnergizes in series with relay 211, with sequence switch410 in position 12, a circuit is closed from ground, through the contactand armature of relay 400, upper contact 401 (12), conductor 588,contact 534 of register 530 closed in position 3, conductor 535, andthence to conductor 428 (Fig. 4), armature and back contact of the No. 3counting relay 429, winding of the No. 3 relay 430, to battery andground. Relay 430 attracts its l,armature and prepares a locking circuitfor itself, in series with the winding of relay 429. As the brush 218encounters the first segnient of the commutator 220, relay 400 lisreleased to permit the energization of relay 429. @n the nextenergization of stepping relay 400, the stepping circuit is extended byway of conductor 428, armature and front contact of relay 429, armatureand back contact of relay 424, winding of relay 425, to battery andground. Tn asimilar manner the No. 2 counting relays and each followingpair of counting relays are energized and locked up in response to theoperation of stepping relay 400. `When the 0 counting relay 420 ishnally energized,

the fundamental circuit is opened and a circuit, including up erright-hand Contact 407 (12), is closed switch 410 out of position 12 andinto position 14. As soon following the opening of the fundamentalcircuit at the sender, as brush 218 engages an insulating segment ofcommutator 220, the holding circuit of relay 211 is opened. Relay 211releases its armatures and opens the circuit ofV the updrive powermagnet 213, bringing the brushes 225,226 and 227 to rest in operativerelation to the selected group of outgoing trunks. Relay 211 alsocompletes a circuit from battery, through the winding of sequence switchmagnet 210, lower righthand contact 204 (4), backI contact' andleft-hand armature 'of relay 211, to ground.

Sequence switch 210 advances into position 5.

In position 5 of sequence switch 210, relay 211 is immediately energizedin a circuit from battery through the left-hand winding of said relay,upper left-hand contact 229 (5 to 7 lower left-hand contact 229 (5), toground. Relay 211 closes a circuit rom battery, through the winding otsequence switch magnet 210, lower lefthand contact 204 (5), frontcontact and left-hand armature of relay 211, to ground, for drivingsequence switch 210 out of position 5 and into position 6. Relay 211remains energized in position 6 of the sequence switch, provided theirst trunk in the selected groupy` is busy at this time. The holdingcircuitfor relay 211 may be traced from battery through-fthe righthandwinding, front contact and inner right-hand armature of said relay,outer right-hand armature and contact of relay 211, upper left-handcontact 207 (5 to 18), upper rightfJ hand contact 207 (5 to 6i), testbrush 227, test terminal 224, and thence to a multiple of test terminal224 at some other switch, brush 227 of such other switch, to ground at)the upper right-hand contact 206\(6 to 8i completes a circuit frombattery through thev winding of the up-drive power magnet 213,Aright-hand contact 205 (6), front contact and left-hand armature ofre1ay 211, to ground. Switch shaft 215 is advanced upward in lthe ltrunk-hunting movement. When an idle trunk is reached the holdingcircuit of relay 211 is opened, since no A=ground is found on the testterminal 224.

The following substitute circuit, however, is maintained closed toprevent the immediate 'l release of relay 211. VBattery, through theleft-hand Winding of said relay, upper lefthand contact 229 (5 to 7),upper right-` hand contact 229 (5% to 6), centering cornmutator 221,brush 216, to ground.` This circuit is closed until'the brushes 225,226y and l227 are accurately centered on the terfor driving sequenceRelay 211 by remaining energized,

minals of the idlev trunk, at which time brush 216 engages an insulatingsegment of commutator 221. Relay 211 thereupon releases and opens thecircuit of the updrive power magnet 213. Relay 211 also closes a circuitfrom battery, through the winding of sequence switch ma et 210, lowerright-hand contact 204 (6), back con tact and left-hand armature ofrelay 211 to ground. Sequence switch 210 advances from position 6 intoposition 7. On rea-ching position 6%, sequence switch 210 closes itsupper right-hand Contact 206 to apply a busy ground potential to thetest ter' minal 224 of the selected trunk. Relay 211 is againimmediately energized by means ofl a circuit from battery, through itslefthand winding, upper left-hand contact 229 (5\ to 7 lower left-handcontact 229 (7 toJ ground. Relay 211 completes a circuit from batterythrough the winding of the sequence switch magnet 210, lower left-handcontact 204 (7 front contact and left-hand armature of relay 211 toground. Se uence switch 210 advances into position 8. elay 211 remainsenergized in positionl 8 of sequence switch 210 by means of a circuitfrom battery through the right-hand winding, front contact and inner.right-hand armature .of relay 211, outer right-hand armature and contactof said relay, upper left-hand contact 207 (5 to 18), lower left-handcontact 207 (7 toy 18), conductor 202, terminal 136, brush 144, upperrighthand contact 119 (9 to 1611), lower left-hand contact119 (10L to18), to ground. The district and oiiice switches having been positionedin the manner described a trunk circuit 700, 701 is selected leading toa mtnual operators position in the distant o ce When the sender sequenceswitch 410- reaches position 14, after the completion of oilice groupselection, a circuit is closed from ground, 'through contact 408 (14),upper eft-hand contact 316 (10), winding of sequence switch magnet 310,to battery and ground. ySequence switch 310 moves out of position 10 andinto position 11. A circuit 1s now completed vfrom battery through theback contact and inner lower armature 0* relay 725, (Fig. 7 conductor731, righthand winding of` relay 713, winding of relay incense 1451i),lower contact 323 (11), brush 306, terminal 301, conductor 138, lowercontact 125 (11), brush 143, terminal 135, conductor 201, upper contacts209 (8), brush 226, terminal 223, conductor 701, inner armature and backcontact of relay 708., inner armature and back contact of relay 717,outer normal contact ot' relay 716, left-hand winding of relay 713, toground. Relay 713, being marginal, does not energize in series withresistance 419. Relays 714 and 412, however, energize in the circuittraced. Relay 714 closes a circuit trom ground, through its` armatureand contact, winding of relay 715, to battery and ground. Assuming thatplug 726 of the trunk circuit has not been removed from the jaclr by theoperator after the termination of a prior call, relay 710 will beenergized by means of a circuit to be hereinafter described. Hence whenrelay 715 operates, it closes a circuit for itself from battery, throughthe winding and contact and inner left-hand armature of said relay,front contact and outer upper armature of relay 710,

back contact and inner left-hand armatureV ot relay 712, to ground.Relay 715, at its right-hand armature and contact, shunts out the relay714, permitting the latter relay to release. Relay 715 also closes acircuit from battery, through the assignment lamp 711, outer right-handarmature and back contact of relay 7 05, right-hand armature and contactof relay 704, contact and outer left-hand armature of relay 715, toground. The illumination of lamp 711 informs the operator that a call iswaiting on the corresponding trunk.

1t, however, the plug 726 is not inserted in a line jack at the time thetrunk 700, 701 is seized, relay 710 is deenergized and relay 715, indingno locking circuit, again releases as soon as relay 714 has been shuntedout. Referring to Rig. 4, relay 412 which energized in series with relay714 completes a circuit trom battery, through the winding of relay 411,armature and contact of relay 412 to ground. Relay 414 is energized atthe-same time by means of a circuit from battery, contact 415 (14 to16), winding of said relay, armature and contact of relay 412, toground. Relay 411, at its lowerinost armature and front Contact, closesa circuit including contact 409 (14), for driving the sender sequenceswitch 410 out of position 14 and into position 16. As the sequenceswitch 410 reaches position 14%, the circuit above-traced through theright-hand winding ot marginal relay 713, over the upper or tip side ofthe line to lower contact 324', is now extended by way of lower contact406 (14% to 156), innermost armature and front contact of relay 411,winding of relay 412, contact and armature of relay 414, tront contactand middle armature of relay 411, lower contact 405 (145, to 16), lowercontact 323 (11), and thence over the ring side ot the line to ground atthe left-hand winding of marginal relay 713. 1t will be observed thatthe resistance 419 has been excluded from this latter circuit. Relay713, therefore, becomes energized and completes a circuit from battery,through the winding of relay 712, to ground at the contact and armatureof relay 713. Relay 712 closes a circuit in shunt of relay 714 as`follows: battery, back contact and inner lower armature of relay 725,conductor 731, righthand winding of relay 713, contact and outerleft-hand armature of relay 712, inner normal contact of relay 716, andthence over the tip side of the line and returning as described, toground at the letthand winding of relay 713. Relays 714 and 715,therefore, remain deenergized. Relay 712 completes a circuit frombattery through the assignment lamp 711, outer right-hand armature andback contact of relay 705, right-hand armature and Contact ot relay 704,Contact and inner upper armature of relay 710, contact and innerright-hand armature of relay 712, to ground. rilhe lamp 711 isilluminated and the operator, observing the same, knows that a call isawaiting her attention.

At her convenience the operator responds to the call by depressing thehome assignment key 703 which -is individual to the trunk 700, 701.Thekdepression ot key 703 operates to associate the trunk with the callindicator mechanism at the home operatorie position. A circuit is closedfrom battery through the winding of relay 81.18, conductor 732, contactand outer lower armature ot ref lay 710, right-hand winding of relay 705, contact of key 703, conductor 733, armature and contact of relay823, back contact and ri hthand armature of relay 821, to ground. elay705 energizes and loclrs up in a circuit from battery through thewinding oit relay 818, conductor 732, contact and outer lower armatureof relay 710, windings ot relay 705, in series, contact and lett-handarmature of said relay to ground. Relays 705 and 818, therefore, lock upindependent ot the key 703 which restores as soon as itis released bythe operator. Relay 705 closes a circuit from battery through the lamp711, outer right-hand armature and liront Contact ot relay 705,interruptor 734, to ground. Lamp 711 is caused to dash in the circuittraced. Relay 705 also closes a cir- 4cuit from battery through thewinding .oit relay 708, contact and inner right-hand armature of relay705, conductor 735, winding of relay 823, back contact and lett-handarmature of relay 821, to ground. Relay 708 attracts its armatures andentends the incoming trunlr conductors 700 and 701 by` way of conductors736 and 737 to the operating relays 801, 800 and 802 ot the calliesindicator mechanism. Up to this time, relay 412 at the sender has beenenergized in series with relay 713. l/Vhen relay 708 attracts itsarmatures the battery supply through the windings of relay 713 isdisconnected from conductors 700 and 701 and relay 412 deenergizes. Therelease of relay 412 opens the circuits of relays 411 and 414,permitting these relays to become deenergized. Relaysv713 and 712` atthe trunk circuit, are also deenergized at this time. Re-

' lay 411 completes. a circuit from ground,

l ductor 736.

' opposite direction.

ent upon which pole of battery is connected tol a given side of theline. They may be also weak or strong, dependent upon whether a high orlow resistance is included in the circuit. Relay 801 is polarized insuch a manner as to respond only to an impulse created by a liow ofcurrent from the positive pole of battery over the conductor 737 andreturnin toground by way of conhe relay 800 is polarized in such amanner as to respond only to an impulse created by a flow of current inthe Relay 802 responds to strong im ulses of both positive and negativepolarity but,'being marginal, does not operate on weak impulses.

When the impulse sequence switch 610 reaches position l, a circuit isclosed from ground, which represents the positive pole of battery, uppercontact 608 (1% to 2), conductor 620, back contact and inner armature ofrelay 411, lower contact 406 (14?, to 16), lower contact 324 (11), andthence over the upper or tip side of the line to conductor 736, windingsof relay 801, 800 and 802 in series, conductor 737, and returning overthe rin 323 (11?, lower contact 405 (14%; to 16), middle armature andback Contact Voi relay 411,

. conductor 621, upper contact 613 (l,L to 2),

high resistance 614, conductor 622, lower Contact 418 (16), to thenegative pole of battery. Owing to the high resistance 614, this impulseis weak in character and is of such polarity as to cause theenergization of relay 800. Relay 800 attracts its armature and closes acircuit from battery through the left-hand winding of relay 804,lefthand winding of relay 805, back contact and side of the line tolower contact.l

left-bandarmature of relay 804, contact and armature of relay 800,conductor 843, lefthand armature and contact of relay 818, contact andouter left-hand armature of relay 819 to ground. Relay 805 energizes andcloses a circuit from battery, through the letthand winding of relay804, left-hand winding of relay 805, riehtfhand winding of relay 804,contact and inner right-hand armature of relay 805, to the groundedconductor 843. Relay 804 however does not energize since its right-handwinding is shunt-l ed out at this time by the direct path through thearmature and contact of relay 800 to the grounded conductor 843. Relay805 closes a circuit from battery, through the winding of relay 808,back contact and inner armature of relay 807, contact and outerright-hand armature of relay 805 to the grounded conductor 843. Relay808 attracts its armature and closes a circuit from battery through thewindings of relays 808 and 807 in series, Contact and inner righthandarmature of relay 808 to the grounded conductor 843. Relay 807, however,does not energize since its winding is shunted out by the direct path toground, through the contact and outer right-hand armature of relay 805.As soon as sequence switch 610 leaves position 2, relay 800 releases andremoves the shunt path from around the right-hand winding' of relay 804.Relay 804 thereupon energizes in series with relay/7805.

hile sequence switch 610 passes through positions 3?; to 3% a circuit isclosed from the positive le of battery, upper contact 608 (3;,L to 3%conductor 620, thence over the tip side of the line through relays 801,800 and 802, returning over the ring side ofthe line to conductor 621,upper contact 613 (32 to 3%), high resistance 614, conductor 622 to thenegative pole of battery at the contact 418. This causes another weakimpulse to be sent of the proper polarity for energizing the polarizedrelay 800. Relay 800 attracts its armature and closes a circuit frombattery through the left-hand winding of relay 804, front contact andleft-hand armature of said relay, contact and armature of relay 800 tothe grounded conductor 843. This dlrect circuit to ground shunts out theleft-hand winding of relay 805 causing this relay to deenergize. Relay805 releases its armatures but a shunt circuit is maintained around thewinding of rela 807 as follows: battery, through the winding of relay808, back contact and inner armature of relay 807, Contact and innerright-hand armature of relay 804 to the grounded conductor 843. Whensequence switch 610 moves out of position 3%, relay 800 releases itsarmature and opens the circuit through the left-hand winding of rela804. Relay 805, being deenergized, no ot er circuit is offered for re-

